Make Board more generic

[makingthematrix]

Suggested direction of work:

1. Create a common trait for boards.
2. Move Board.id from the Board companion object to the Board class, and its declaration to the trait.
3. Let the torus be the default topology of the board (ie. if the creator of the automaton doesn't not specify otherwise, this is what they will get).

In the end it should be easy to create boards with "planetary" and flat surfaces, as well as custom ones.